Recent patent literature has disclosed technologies for a photographic element having a transparent magnetic recording layer for information and data recording and reading purposes. For example, U.S. Pat. No. 5,254,449 discloses the preparation and use of a substantially transparent magnetic recording layer in a novel photographic element. U.S. Pat. Nos. 5,427,900 and 5,432,050 describe transparent magnetic recording layers for use in photographic elements wherein organic solvents are used for the preparation of a dispersion containing the magnetic particles. U.S. Pat. No. 5,457,012 describes a magnetic recording layer formed from a dispersion of magnetic particles in an aqueous medium. The photographic element and particularly the transparent magnetic recording layer provided thereon must be capable of repeated use in both the recording and reading mode and, therefore, must be durable, abrasion resistant and scratch resistant so as not to adversely affect the quality of the photographic element. For example, during the residence of the film in a camera, entries may be made to the magnetic recording layer for every exposure, and an indeterminate number of read operations are conducted depending on the particular application to which the film is used. This also is true in the processing of the film and in subsequent use of the processed film for additional copies, enlargements and the like.
When a transparent magnetic recording layer is used as the outermost backing layer, excellent lubrication at its surface is required to lower the contact friction with the magnetic head and to allow for multiple transports of the film through various magnetic head-containing equipment. A lubricant could be added directly to the transparent magnetic layer. However, this typically weakens the layer and may result in premature rupture of the layer and loss of signal or recorded information. Furthermore, when the lubricant is added directly into the magnetic layer and coated and dried, the lubricant will be distributed throughout the magnetic layer and may not reside primarily at the surface where it is required for optimal performance. Alternatively, a separate lubricating layer is applied on the transparent magnetic recording layer. This of course reduces the manufacturing efficiency of the product by requiring several coating stations.
When a photographic element having a transparent magnetic recording layer as the backing layer is subjected to ordinary processing steps that differ from those related to ordinary magnetic tapes (e.g. audiotapes, and videotapes), new problem arises that staining materials, composed of ingredients in a developing solution, adhere to the back surface of the photographic element, and the said staining materials are transferred to the surface of a magnetic head at the time of the magnetic recording or reproduction after processing, which results in an error of magnetic input/output (an error in magnetic recording/reproducing). In order to solve such a problem, it is also effective to incorporate, into a backing layer, abrasives that are well known in the field of magnetic tape, for a silver halide photographic light-sensitive material having a transparent magnetic recording layer.
U.S. Pat. No. 5,798,136 describes a method of producing an imaging support which includes providing a support, simultaneously coating on a side of the support; a transparent magnetic recording layer comprising magnetic particles, abrasive particles, a polymeric binder and an organic solvent, and a lubricating overcoat layer farthest from the support, the lubricating overcoat layer comprising wax particles having a size from 0.01 to 0.5 micron, and an organic solvent; and drying the magnetic recording layer and the lubricating overcoat layer. If the wax is dissolved in a solvent and coated simultaneously with the oxide layer, it can diffuse into the magnetic layer before the coating is dry. Thus, the amount of lubricant remaining at the surface is inadequate for proper lubrication. Since the diffusion rate is inversely proportional to the size of the dissolved lubricant, the wax dispersions, which are particles of sizes that are much larger than the radius of a dissolved long chain fatty acid or polymer, tend to remain at the surface during the coating process and provide adequate lubrication in the dried layer.
Aqueous wax dispersions of colloidal sizes (0.01 to 5 micron, typically in the range of from 0.01 to 1 micron) are generally known. Non-aqueous wax dispersions of colloidal sizes are difficult to prepare. Wax can be compounded into viscous non-aqueous media (viscosity greater than, for example, 1000 cps) by mechanical force. The problem with such an approach is that the particle size is difficult to predict and more difficult to reproduce. The resultant dispersions are not truly colloidal dispersions and on dilution wax particles will settle down or precipitate out. U.S. Pat. No. 5,798,136 has disclosed the preparation in acetone/methanol mixed solvents of polyethylene wax dispersions by first diluting the aqueous dispersions after dialysis. It has also disclosed the preparation of Carnauba wax dispersion in isobutyl alcohol by further ground using a ball mill wax particle having an original size of greater than 2 microns.
U.S. Pat. No. 5,776,668 describes a photographic element having an outermost lubricant layer comprising a lubricant, a water-dispersible polymer as a film forming binder, and abrasive particles having a Moh's scale hardness value of at least 6.
This invention provides a photographic element having a transparent magnetic layer with a lubricant layer formed from a nonaqueous coating composition. The resultant photographic elements demonstrate excellent optical properties and improved magnetic performance and running durability.